I'm also wondering why NASA didn't stuck at one project, but instead cancelede and begun from scratch many times.
First the X-33, which i found absolutely staggering.
Now they're doing this Apollo-ish thing which should be used to bring stuff and personnel to the moon, and a reusable orbiter, basically Shuttle2, which can be mounted on one of those apollo-ish rockets (don't know the name - sorry) instead of using booster rockets like now.